Please add a "fix content length" mutator

99% of the time I create an HTTP::Response I forget to set the Content-Length header, thus stalling the HTTP pipeline. To fix this one simply has to remember to

$resp->content_length( length $resp->content );

Which is reasonable enough if you have the response in a variable. However, #135 wishes to add chaining mutators in order to support fully-constructing a response object in a single expression without needing such a temporary. Without it it becomes hard to fix the content length.

I'd therefore suggest either a special "fix the content length" method, or else the default behaviour of a ->set_content_length method with no additional arguments, to do this.

return HTTP::Response->new( 200 )
    ->set_content( join "\n", @lines )
    ->set_content_length;

Start with the HTTP::Response mutator entry points and read issue #135 for the intended chaining behavior. The work is done when a response can derive its Content-Length from its content through the proposed chained API, with the behavior covered by the project's existing tests.